Re: Object Class and Data Type

DEC RDB supported domains (called global fields) way back in 1983. But it
did not prohibit joins across domains. In 1986, when they added support
for SQL, they put in a create domain command.

However, it was easy to find joins across domains by a query on the
metadata.

I haven't tracked RDB since 2001, so they may have added it.

The reason I ask is that DEC's data dictionary at first made the record the
most basic dictionary item. There was a huge debate, and eventually the
domain was added as the fundamental lexical entry.

IIRC, Martin wrote on this subject, back in the 1970s.

Now I have two other questions:

First, when did CREATE DOMAIN make it into mainstream SQL? Second, does the
relational model have an equivalent concept? I would think it would have
to, given the definition of a relation.
Received on Mon Apr 05 2004 - 14:45:02 CEST